1. Field of the Invention
This invention relates to a radio data transmission apparatus, and more particularly to a radio data transmission apparatus for receiving a message having a code number.
2. Description of the Related Art
A message information receiving apparatus for receiving various kinds of message information using a mobile FM teletext broadcasting has been disclosed in, for example, Japanese Unexamined Patent Application No. Hei 8-149028.
FIG. 1 is a block diagram showing an example of such conventional art. Referring to FIG. 1, the receiving apparatus comprises a FM radio section 20 for receiving FM broadcasting radio wave and making voices and a message information reception processing section 30 for carrying out various processings for the message information multiplexed in FM broadcasting radio wave received by the FM radio section 20.
The FM radio section 20 comprises an antenna 21 for receiving FM broadcasting radio wave, a FM tuner 22 for tuning the FM radio broadcasting, a FM demodulator 23 for demodulating FM signal, a stereo demodulator 24 for converting the demodulated FM signal to stereo signal, a pair of amplifiers 25a, 25b for amplifying an output signal of the stereo demodulator and a pair of speakers 26a, 26b for outputting the signal amplified by the amplifiers in the form of voice.
The message information reception processing section 30 is connected to the aforementioned FM demodulator 23 and comprises a L-MSK (level controlled minimum shift keying) demodulator 31 for separating the message information multiplexed in the FM broadcasting radio wave, an error correcting decoder 32 and a reception processing portion 33 for performing various kinds of processings for the separated message information.
To this reception processing portion 33 are connected a ROM 47 storing a processing program, a key input portion 43 which is an input means for a destination number, a code number and message information, a display unit 48 which is a display means for displaying the message information and the like, a card processing portion 45 for performing read/write for an IC card 46, a RAM 44 for storing the received message information, input data from the key input portion 43 and the like, a sound dispatching portion 42 for dispatching a sound corresponding to a result of processing by the reception processing portion 33, and a reception control portion 41 for tuning reception of the FM tuner 22.
FIG. 2 is an example of a transmission signal format of the message information for FM-multiplexing a pager program.
A program number xe2x80x9c250xe2x80x9d indicates that this message information is a pager program and an identification code xe2x80x9c[xe2x80x9d indicates a type (a number inherent of an apparatus or a number determined freely) of the pager number. The message information includes xe2x80x9cdestination numberxe2x80x9d, xe2x80x9ccode numberxe2x80x9d and xe2x80x9cmessage contentxe2x80x9d.
Next, operations will be described.
If the message information receiving apparatus receives FM multiplexed broadcasting, the L-MSK demodulator 31 separates the transmission signal. In the FM multiplexed transmission signal, the pager number (destination number+code number) are compared with the destination number and code number stored in the RAM 44, and only when it coincides therewith, the sound dispatching portion 42 dispatches the sound and the message content is displayed on the display portion 48.
However, as for the conventional message receiver capable of displaying characters like a pager and the like, when a transmission side transmits a character message thereto, other people than a person of a destination of the message may see it. Because of telephone number input error upon transmission of a message, use of a receiver by other people without permission and the like, a message may be seen by other people whom a transmitter does not imagine.
Further, in a case when a single message receiver is shared with persons, a message can be read by anybody because a destination of the received message cannot be distinguished, so that confidential treatment for allowing only a particular person to read cannot be carried out.
Further, because a received code number coincides with a stored code number, the received message is displayed, and therefore despite provision of the code number, other people than the particular person can read the message.
Accordingly, an object of the invention is to provide a radio data transmission apparatus capable of protecting privacy of a message transmitter provided that an improper message is sent, a receiver is used without permission of an owner or a receiver is shared among plural persons.
In the radio data transmission apparatus of the present invention, the message is scrambled when it is transmitted. The message is provided with a code number which is a key for releasing the scramble. The message and code number are both scrambled and sent to outside.
A receiving person is notified of the code number contained in transmission data by a transmitting person. If data is received, the receiving person inputs the notified code number so that a scrambled code of the code number is compared with the code number contained in the transmission data. Then, whether or not the scramble should be released is determined. If both the code numbers coincide with each other, the scramble of the data is released and the message is displayed. If they do not coincide, the data is displayed as it is.
Preferably, this radio data transmission apparatus comprises an input portion for inputting a message and code number, a scramble generating portion for scrambling entire transmission data containing the code number at the time of transmission and further scrambling a code number input for unscrambling at the time of reception, a comparing portion for comparing a code obtained by scrambling a code number input by the receiving person from the input portion at the scramble generation portion, a unscrambling portion for unscrambling the reception data when they coincides with each other as a result of the comparison and a display portion for displaying a message.
In the radio data transmission apparatus of the present invention, by providing transmission data with a code number for unscrambling the transmission data as well as the message, only a person permitted by the transmitting person (person knowing a code number attached to the message) can make the code numbers coincide with each other at the comparing step and then unscramble and display the data.
Further, because the code number aims at unscrambling the transmission data, even if data is displayed as it is although the code numbers do not coincide at the comparing step, the displayed data cannot be read because the scramble has not been released. Thus, there is no problem in viewpoints of security. Conventional data having only message information is not scrambled because no code number is contained, and that data can be displayed promptly, so that the scrambled data and conventional data can be handled in the same manner without any distinction.